The present invention generally relates to pool safety equipment. More particularly, this invention relates to a method and unit for preventing an obstruction from being trapped by suction to an inlet of a pool filter pump system. The unit can be mounted directly to a skimmer lid of the pool filter pump system, and operates to vent air into the system when a vacuum level within the system exceeds a specified vacuum limit, as is the case if the drain or another inlet connected to the system is partially or completely obstructed, such as by a child or foreign object.
To maximize enjoyment and maintain proper sanitary conditions, swimming pools must be constantly cleaned of debris, dirt and other contaminants. Such a requirement is particularly demanding in the case of commercial pools and hot tubs that are likely to be used by a large number of people. For most pools and tubs (hereinafter simply referred to as pools for convenience), the primary task of cleaning is performed by a filter pump system that continuously draws water through a drain located at the bottom of the pool, typically at or near its deepest point, and through a number of suction lines located elsewhere, typically along the perimeter of the pool. As with all pools, but particularly commercial pools, a high rate of water flow must be achieved through a suitable filtering medium in order to maintain an acceptable level of cleanliness. Consequently, a high capacity pump must be employed to draw the water from the pool, with a relatively larger pump generally being required as the size of the pool increases.
A significant hazard with the use of such large filter pumps is the potential for individuals and particularly children to become drawn and trapped against the drain or a suction line as a result of the vacuum created by the pump when the drain or suction line inlet is obstructed. Occurrences of this type of accident have caused the pool industry to look for solutions. One approach has been to modify the drain construction, examples of which include U.S. Pat. No. 4,658,449 to Martin, directed to a protective adapter for covering a pool drain, and U.S. Pat. No. 3,940,807 to Baker et al., directed to modifying the drain opening itself in order to more uniformly distribute the flow of water toward the center of the drain. While such approaches may be acceptable for many pool applications, a solution that is capable of being retrofitted to an existing pool without altering the appearance, size or construction of the drain is often more desirable and practical. Furthermore, these solutions only reduce the suction level at the drain, and safer operation of a pool can be achieved if the dangerous suction condition at the pool drain is completely eliminated if the drain is obstructed by a child.
As a solution, vacuum relief valves and units for preventing a child or an object from being trapped by suction to a drain or any other suction line are taught in U.S. Pat. Nos. 5,682,624 and 6,251,285 to Ciochetti. The valve taught by U.S. Pat. No. 5,682,624 is configured for mounting directly to a suction line between a drain or suction line and the filter pump, while the valve taught by U.S. Pat. No. 6,251,285 is configured for installation as a lint trap cover on an otherwise conventional lint trap unit located upstream of a pool filter pump. Both valves generally operate by causing the filter pump to quickly lose its prime when a child or object obstructs or becomes trapped against the drain or suction line inlet, so that the vacuum created by the filter pump is completely eliminated. In particular, the valves permit air to rapidly flow into the drain and suction lines if a predetermined vacuum level is exceeded within these lines, as is the case if the drain or one of the pool's suction line inlets becomes partially or completely obstructed. The rapid influx or venting of air eliminates the vacuum within the lines and, therefore, the resulting unsafe condition. The response of the valve is preferably damped such that the valve will remain open sufficiently long to cause the filter pump to completely lose its prime.
Operational aspects of certain vacuum relief valves currently on the market include the ability to be locked in the open (venting) position to allow for the release of an obstruction without time constraints. Such valves do not reset themselves, but must be manually reset in order for the pump to return to normal operation. However, a valve can be unnecessarily actuated by a transient vacuum spike (pressure drop), for example, during pump startup, and certain valves may have a tendency to rapidly open and close during pump startup. Furthermore, pump damage can occur if the pump continues to run when the valve is locked open and continues to vent air into the pump.